Mailing Lists: Apple Mailing Lists
Image of Mac OS face in stamp
 
[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: SMPTE parsing algorithm?

Correct on both counts; however, I believe the existing algorithms are correcting for non-locked sample frequency clocks which are high frequency and low jitter. The output from parsing LTC is low frequency and high jitter. It is possible in a post processing environment: You could low pass the frame clocks with a massive FIR low pass filter to get rid of jitter and compensate for the delay by shifting samples. You still have the problem of picking the corner frequency that responds to speed variations fast enough, but doesn't let jitter through. Given that the audio quality is compromised by gunky heads, too, it would seem to make more sense to redo the transfer.

2008/1/14, Herbie Robinson <email@hidden>: 
 They can be filtered to average them out, but that probably won't be
 any good for driving a time stretching algorithm to compensate for
 local variations (I'm guessing that's what you are thinking about
 doing?).


I think you're talking about "varispeed" here... Time stretching would
preserve pitch, which would result in the corrected track having the
right timing but variations in pitch.

Btw. there was some free sample code somewhere which demonstrated the
capabilities of the CAClock class for exactly this purpose. I'm pretty
sure Bill and the others from the CA team know where it can be
found...

--th

At 1:30 AM -0500 1/14/08, Jaime Magiera wrote:
If the tape was gunky, the LTC is going to have problems as well. Yikes, that's 2400 possibilities for error per second. Good luck.

If tape was that bad, the audio would probably be audibly compromised. LTC will actually survive encoding as 128Kb MP3, but not much more than that (surprised me, too).

Does sound like this LTC track might make a nice test case.
--
-*****************************************
**  http://www.curbside-recording.com/  **
******************************************
_______________________________________________
Do not post admin requests to the list. They will be ignored.
Coreaudio-api mailing list      (email@hidden)
Help/Unsubscribe/Update your Subscription:
http://lists.apple.com/mailman/options/coreaudio-api/email@hidden

This email sent to email@hidden
References: 
 >Noob Questions (From: Matt Mashyna <email@hidden>)
 >Re: Noob Questions (From: Jens Alfke <email@hidden>)
 >New to converter. (From: Aurélien Ammeloot <email@hidden>)
 >Re: New to converter. (From: John Draper <email@hidden>)
 >Re: New to converter. (From: Michael Thornburgh <email@hidden>)
 >SMPTE parsing algorithm? (From: "Kevin Dixon" <email@hidden>)
 >Re: SMPTE parsing algorithm? (From: Jaime Magiera <email@hidden>)
 >Re: SMPTE parsing algorithm? (From: "Kevin Dixon" <email@hidden>)
 >Re: SMPTE parsing algorithm? (From: "tahome izwah" <email@hidden>)



Visit the Apple Store online or at retail locations.
1-800-MY-APPLE

Contact Apple | Terms of Use | Privacy Policy

Copyright © 2007 Apple Inc. All rights reserved.